IIRC,some of the hotter running HD7870 cards drew more power even though they had the same clockspeeds,GPU voltage and PCB as other models. If custom cooled models do run cooler,I expect lower power consumption,unless these cards are pre-overclocked above 1GHZ.
Having said that the R9 290 sample TPU tested,had power consumption which was not much more than a GTX780,Geforce Titan or HD7970GE:
http://www.techpowerup.com/reviews/AMD/R9_290/24.html
They also only look at graphics card power consumption.
Also,they tested another R9 290X sample,which was from Sapphire and not AMD,and it consumed much less power too:
http://www.techpowerup.com/reviews/P...90X_OC/24.html